Well-Formed Code

As you've already noticed, the exceptions and variations on these basic XHTML fundamentals sometimes appear to be vague.

This especially becomes problematic when using software applications that don't take the rules of XHTML into account and throw out syntactical rules. Someone studying the output of a WYSIWYG application will often learn bad code. In XHTML, this is especially problematic, because to be a valid XHTML document, the syntax rules must conform.